The incredible journey of the monarch butterfly

Saturday

Sep 27, 2008 at 12:01 AMSep 27, 2008 at 6:19 AM

The monarch butterfly settling in for a soft landing on the purple and gold blooms of New England aster is making one of the first pit stops on an incredible journey. That’s because the monarchs seen in increasing numbers as fall arrives are headed for wintering grounds in Mexico — a journey that may take more than a month.

Chris Young

The monarch butterfly settling in for a soft landing on the purple and gold blooms of New England aster is making one of the first pit stops on an incredible journey.

That’s because the monarchs seen in increasing numbers as fall arrives are headed for wintering grounds in Mexico — a journey that may take more than a month.

No other butterfly migrates like the monarch. Some — like the painted lady — wander north every year, but can’t survive winter and die back when it gets cold.

Those that withstand Midwestern cold do so by spending the winter in the chrysalis stage. Some, like the regal fritillary, hatch as caterpillars in the fall and seek cover in grass and leaf litter on the ground and enter diapause — a state where they slow their body functions during winter.

That monarch sipping nectar in a restored central Illinois prairie patch is part of a migration cycle that takes at least three generations.

“Right now you see them gliding around all over the place — that’s the mobile generation,” says Michael Jeffords, an entomologist with the Illinois Natural History Survey in Champaign. “There are other generations over the summer. However, the last one doesn’t reproduce, but heads on south.”

Jeffords traveled to Mexico last winter to visit monarch butterfly refuges and take hundreds of photographs.

Most butterflies live only a few days or weeks. They live long enough to mate and lay eggs. They generally die when their fragile wings wear out.

But monarchs need to live long enough to complete their life’s journey — a trip that can be long and dangerous.

Jeffords says storms are a constant threat, as is the loss of places to rest and refuel.

“If you’ve flown over this part of the country, you know that just finding safe haven to congregate and rest can be a challenge,” he says. “They have to find nectar sources along the way, too — you’ve got to be able to fuel up.

“There are very few places to rest safely.”

Tim Cashatt, chair of zoology at the Illinois State Museum, says monarchs face a variety of hazards but have developed defenses to help keep them alive.

“A lot of them get hit by cars on the road, and weather as much as anything is a problem, including storms,” he says. “But over the millions of years they have survived, they obviously have some built in ways of dealing with weather that has allowed them to survive.”

Monarch caterpillars are unpalatable to birds thanks to their food, plants of the milkweed family. Most would say the caterpillars — and hence the adults — taste bad to birds.

“But birds have a pretty poor sense of taste,” says Cashatt. “When they eat a monarch and it does end up in the crop, that particular chemical causes a problem and they vomit it up.

“It leaves enough of an impression that birds learn to avoid (monarch butterflies).”

Still, millions of monarchs make it to forests in the mountains near Mexico City, where the climate is cool and protective.

Most of the monarchs in the eastern United States head to Mexico, but a small band winters in Florida. In the western U.S., monarchs winter in California.

Jeffords says the forests in Mexico where monarchs find sanctuary are threatened by logging.

“The microclimate is cool, but historically it doesn’t get cold enough to freeze,” he says. “They spend the winter there in relative peace. On warm days, they may fly out and get a drink or seek nectar.”

A microclimate is a specialized environment that provides the exacting conditions some organisms need to live. Think of the north side of the house where snow is slow to melt — even on a sunny day. That is an example of a microclimate.

But if too many trees in the forest are cut, it may change the equation for the monarch.

“If they have a freak snow storm or cold snap, they aren’t as protected anymore,” he says of losing portions of the forest to logging. “They could freeze.”

After spending the winter, monarchs mate and lay eggs on the return trip north.

“They usually hang around the Gulf Coast and lay eggs, and another generation makes the rest of the way northward,” Cashatt says. “It may take another generation for them to reach, say, Michigan.

“And the next generation is the one that flies south.”

Jeffords says the odds are long that the monarch seen in the prairie this week makes it back.

“Occasionally, one will,” he says. “You’ll see one that is beat all to heck, and you’ll think, ‘That one made it all the way back.’

“It’s a pretty rigorous trip.”

In central Illinois, people can give monarchs a helping hand by planting fall-blooming wildflowers like asters.

“New England asters are great,” Jeffords says. “(Monarchs) need the fall asters and gentians and rough blazing star and all those late-blooming plants.

“Prairies pretty much bloom yellow in fall, and any of those flowers are good nectar sources.”

Jeffords says old-fashioned sedums — known as heirloom plants — are popular with butterflies.

“Mine are covered with painted ladies at the moment.”

Creating a refuge for butterflies to rest and refuel can help compensate for losses elsewhere.

“The cumulative environmental stress and cumulative environmental facilitation — they can cancel each other out,” he says. “If you’ve got a patch of goldenrod on the fence row, leave it. All these things make a difference.”

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